Multiple switch-board busy-test circuit and apparatus



(No Model.) 2 Shets-$heet 1. P. A. PIGKERNELL.

MULTIPLE SWITCH BOARD BUSY TEST CIRCUIT AND APPARATUS.

Patented Jan 5, 1892..

2 Sheets-Sheet 2.

(No Model.)

F. A.-PICKERNELL. MULTIPLE SWITCH BOARD BUSY TEST CIRCUIT AND APPARATUS, No. 466,702.

Patented Jan. 5, 1892.

P511719 00., "101cm? UNITED STATES PATENT OFFICE.

FRANK A. PICKERNELIJ, OF NEWARK, NE\V JERSEY.

MULTIPLE SWITCH-BOARD BUSY-TEST CIRCUIT AND APPARATUS.

SPECIFICATION forming part of Letters Patent No. 466,702, dated January 5, 1892. Application filed August 17, 1891. Serial No. 402,901. (No model.)

To all whom it may concern.-

Be it known that I, FRANK A. PIOKERNELL, residing at Newark, in the county of Essex and State of New J ersey, have invented certain Improvements in Multiple Switch-Board Busy-Test Circuits and Apparatus, of which the following is a specification.

This invention relates to multiple telephone switchboards, and especially to busytests adapted for use in connection therewith.

Multiple switch-boards are now almost universally employed in central telephone-exchanges even of moderate size, and wherever employed it is obvious'that for each section some form of busy-test appliance must be pro- Vided whereby an operator at such section may at any time be enabled to ascertain whether a given line called for is or is not already in use at another section of the switchboard. As long as earth-completed circuits only were in use it was not difficult to provide an efficient test; but the use of metallic circuits has made the problem a complex one.

The object of my invention is to provide a test arrangement which shall be simple in construction and operation, reliable in result, and which shall be completely localized-that is to say, that the test-circuit shall be entirely insulated from the line-circuit.

It has been found, also, in multiple switchboards as ordinarily constructed that when a connection is made between any two lines at any section of the switclrboard (the jackframes of the severalsp ring-jacks of each line being permanently connected to serve as one side of the'circuit through the switch-board) a long discontinuous branch remains attached at one end to each of the united circuits, and this being laid up behind the switch-board, with similar branches of other circuits, produces cross-talk due to electrostaticinduction. Another object of my invention is to avoid this disadvantage by so arranging the circuits that when aconnection is made at any springjack the extensions of the line concerned, through the switch-board inwardly, shall be totally out off.

In the accomplishment of the objects stated above my invention consists in a busy-test circuit and apparatus comprising a third wire for each metallic circuit through the switchboard uniting the several spring-jack frames of each line, and a corresponding additional test-wire leading to a battery and earth, provided, in connection with each conn ectingplug and flexible conductor, combined with an operators telephone whose electro-magnetic helix has an earth-wire branched from its center.

It also consists in combining the above instrumentalities with a double separable contact spring-jack for each line at each switchsection, so that wheneveraconnection is made by inserting a plug in a spring-jack the extensions of both sides of the line concerned through the switch-board are totally disconnected.

In the drawings which illustrate this invention, Figure 1 is a diagram showing the testcircuit and apparatus in its simplest form, and Fig. 2 is a similar diagram in which the compound contact spring-jacks are employed to disconnect the inwardly-directed. line-extensions of the switch-board.

The drawing Fig. 1 indicates a multiple switch-board M in three sections S, S and S to each of which are allotted a certain portion of the incoming circuits, so that calls of the said circuits so apportioned are attended to at such section only, while each of the said sections are also provided with spring-jacks or connecting devices for all the lines entering the central station, so that in a manner well understood a call coming in on any line is responded to at its own terminal section only and can there be connected with any line of the system, including those terminating at or responded to at other sections. Each line is represented by a suitable connection device (in this case a spring-jack) at each section and has an annunciator at its ownam swering section only. i I I At each switch-section a suitable key-board is in practice placed with a numberot connecting-conductors having at their two ends connecting-plugs, which, when placed in two spring-jacks representing any two lines, act to unite such lines. By means 'of suitable key devices the operators telephones at each section can be introduced into the circuit of any plug and cord connector,or alternatively a disconnecting-annunciator can be in like manner introduced. In practice there are also ringing keys associated with each connecting-cord, whereby call-signals can be sent over any line to which said cord is attached. In the drawings,forthepurpose of avoiding unnecessary complication, the latter instrumentalities are omitted. I have for the same-reason shown but a single double-plug-connecting conductor and the operators telephones at section S only. Two metallic circuits L and L are shown asentering the central station and are supposed to extend outwardly to exchangestations. The two wires 1 1 of each pass through the several switch-board sections S S S &c., it being of course understood that as the number of entering lines increases the number of sections must also be increased and include in their circuit at the sections where they are respectively terminated their call-annunciators a and a At each section one of the wires 1 loops and the other wire 1 branches into a spring-jack, the construction of which Iwill now explain. The spring-jacks of line L are marked, respectively, J, J and J while those of line L are marked j, 7' and 9' Each jack is provided with a metal frame or stem B, which supports, but is in sulated from, the other work-.

ing parts, and of which the plug socket or sleeve 0 for the reception of the plug-connector is either an integral part or electrically connected thereto. Thisframe by means of an insulating-block 0 supports the j ack-sprin gs or movable contacts 8 and s and the anvil or resting cont-acts t and t and each jack thus comprises a frame terminating outwardly in a plug-socket supporting but insulated from two spring or movable contacts, which, when at rest, bear upon two fixed or resting contacts, from which they are separated upon the insertion into the socket of a suitable plugconne'ctor. It is, however, to be noted that while the resting contact 25 is an electrical contact, whereby the circuit entering the jack is continued in the direction of the jack nextin succession,its counterpart t is non-electrical, and in this case is merely a mechanical stop for the spring 8 Considering first the circuit L,we may trace it through the switch-board as follows: by wire lto contact-spring s and point tat springjack J, wire 2, spring 3 and point t at the second,spring-jack J wire 3, spring-jack J wire 4, call-annunciator a, and then out by wire 1; but from wire 1 branches 5, 6, and 7, normallydiscontinuous, extend to the re spective springs s of the several jacks J, J

, and J for the purpose of enabling any double conductor-plug inserted in the said jacks to connect with this side of the metallic-circuit as well as the other. In the same way the other circuit L passes successively through its series of spring-jacksj, J and j its sidel looping first through jack j, then passing on to wire 8, jack 7' wire 9, jack f, wire 10, annunciator a after which it continues out as 'wire 1, which, as in the first case, has branches 11, 12, and 13 to the second spring t of each of its spring-jacks, and the same mode of connection is carried out irrespective of the number of circuits entering the switch-board.

Each metallic circuit has a third wire to, which traverses the switch-board and which unites electrically the frames or stems of its several spring-jacks, and which has no other connection whatsoever, and thus the jackframes B of circuit L are all united by wire to, while those of circuit L are all united by wire 10 This third wire is a part of the busytest appliance and forms a part of the testcircuit, which, when operated, is capable of being completed by the means I am now about to describe.

At each section is an operators telephone outfit, which can be looped to'anyconnectingcord circuit by means of a suitable loop-key 70 for each of the said connecting-circuits.

In the drawings the telephone-loop endsin two contact-springs f and f and in practice may be of course branched to any number of such contact-springs to serve other pairs of plugs and their cords.

T is the operators receiving-telephone, E the transmitter, and I the transmitter induction-coil, which to maintain a balance is divided, the telephone T being interposed between its two portions 2' and The transmitter E is, as usual, placed in circuit with a local battery I) and with the primary helices of the induction-coil, and for convenience, if desired, a small circuit-opening switch may be added to the circuit. The primary circuit leading from one pole of the battery passes by wire .16 to the primary helix d of one part of the coil "6 to wire 15, to the primary helix d of the second half of said coil by wire 14, to the transmitter E, and thence by way of the switch ,2 to the opposite pole of the battery. From one terminal of the receiving-telephone T a conductor leads by wire 18, secondary helix 6 of one-half iof the induction-coil wire 19 to contact-springfof the loop-key it, where it is ended, and is when at 'rest discontinuous. From the other terminal of the said telephone the other conductor of the telephone-loop leads by wire 20 through the helix e of the second half 2' of the induction-coil and by wire 21 to the opposite contact-spring f of the loop-key 10. From a point at the center of the telephone-helix, or, if it should have two helices, from a point between them, is extended a wire 17, leading to earth at G.

P and P at each switch-section are plugconnectors, forming the terminals of two flexible conductors 26 and 27. They are adapted to be thrust into the plug-sockets constituting the spring-jack frames, and, as is well understood in the art, when so placed in the springjacks of any two lines they serve in conjunction with their connecting-conductors to electrically interconnect the said lines. The plugs P and I have a special construction and have three contact-surfaces all insulated from one another, which respectively make contact with complementary contacts within any spring-jacks into which they may be IIO thrust. The main-line plug-contacts are the tip-contactp, which is adapted to connect with the back springs s, and thereby with one side of the metallic line circuit the first steincontact 11 which is adapted to connect with the jack-spring s and thereby with the other side of the metallic line-circuit, and upon the insertion of the plug not only are these connections made, but the said springs are, moreover, at the same time lifted from their resting-contacts t and 23 I will hereinafter refer to the third plugcontact and its electrical connections. From the tip-contact of plug P the conductor 26 (usually in a flexible cord) extends to the corresponding tip-contact of the other plug P 'of the pair. From the outermost stem-contact p of plug P the conductor 27 extends to the corresponding stem-contact p of plug P The annunciator h is bridged by wire 23-between these plug uniting conductors, connecting therewith at the points as and 00 and it serves to receive signals to disconnect transmitted from exchange-stations. Spring-contacts g and g are suitably mounted within the camloop key in such proximity to the telephoneloop contactsprings f that when the cam is turned down their terminals are just out of connection with each other, but that when the cam is turned into a vertical position they are forced together. These contact-springs g and g are also bridged by wires 24 and 25 between the plug-uniting conductors 26 and 27, so that when the cam is turned up the telephone-loop and telephones are connected across and are brought into communication with the plugs and through them with the spring-jacks and circuits. The third conducting-surface p is also on the plug-stem just behind the surface 19 and on the insertion of the plug in a jack it connects electrically with the socket G, and thereby with the frame B, and the third wire w uniting the said frame with the frames of the other jacks of the said line. From this conducting-surface 19 a wire 28 leads to a testing-battery or other electrical source N, the other poleof which connects with the earth.

One testing-battery by suitable connections, as shown, can be made to supply all of the sections, and so far as the test is concerned the wire leading from the center of the telephone-helix of each operators telephone and that leading from the earth-pole of the testing-battery N, (common to the entire system,) instead of being grounded, may be united to each other.

The operation of the test-circuit is as follows: Line L is in use, the plug P at switchboard section S being inserted in its jack 3' Suppose it to be called for by some subscriber who is connected with another switch-section, the operator at su chsection n1 ust ascertain first whetherline L be at liberty. This is done by first elevating the cam-key It so as to connect the telephone to a particular cord, and then by listening at the said telephone while the plug-socket or jaclcframe of the line desired is touched by the tip of one of the plugs with which the telephone is now connected. If the line required be already busy, a click is heard. If it be at liberty, there is silence, for if a plug be in another socket of the desired line at another section, as shown, alocal circuit is partly formed for the batteryN by way of the earth, battery N, wire 28, plu -contactp on plug P at section S socket and frame B of jack j wire w to socket-frame B of the same line at all other sections, including of course section S. a The touching of the socket-frame B of jack j at section S by the tip of plug P which thus serves as a contact-maker for the local test-circuit, (the telephone being introduced,) completes the said local-battery test circuit through the telephone-helix or a part thereof by way of plug-tip p, conductor 26, junction-point w, wire 24, key-contacts g and f, wire 19, helix 6, wire 18, telephone T, and earth-wire 17 to earth at G, and the establishment of the current of battery Nthrough the telephone necessarily produces a sharp click, which cannot of course appear if the tip of a plug be applied to a jack-frame of a line not in use, and therefore having no connection with battery N. It is evident that this test is equally applicable to central-station switchboards where mixed circuits-that is to say, both metallic and earth-completed circuitsare operated, and although the test-circuit is perfectly localized and is insulated from the line-circuit at all points, and can therefore be depended upon to give an absolutely trustworthy test, no extra appliancessuch as condensers or retardation-coilsare required, and consequently there is no increased complication. It is evident that this busy test can be applied with equal facility to multiple switchboardsinwhichhothsidesarebranchedinstead of one or both being looped into the plug-sockets'. In the arrangement of Fig. 1, however, there is still one defective feature. Suppose that in a multiple switch-board having a considerable number of sections a connection be made with a given line L by inserting a plug into the spring-jack of said line at some section where there are still a number of springjacks beyond. For illustration, we may in stance section S of Fig. 1; but the side Z of L does not loop. It branches into the springjacks. It is evident that, though the insertion of a plug into a jacksay Jactually breaks the circuit on one side Z between 8 and t, it cannot break the circuit on the other side Z, and we then find this condition, that the metallic circuit L, by its two conductors 1 and 1, is united through the two plug-conductors with some other similar line, but that one side of it 1 has a single-wire extension projecting from it at the point 5 and extending from the said point by wire 1 through all remaining sections and annunciater CL and then back through all the jack-contacts of its own line, finally ending discontinuously at the point t of the jack in which the plug is inserted. As this extension lies closely packed among the Wires of other circuits, its electrostatic capacity is high and it introduces inductive disturbance to its own circuit, adjacent circuits acting inductively thereon. To remedy this I arrange the springjacks, as shown in Fig. 2, to cut off both inwardly-direct extensions when a connection is made by a plug. The loop-key and testing-circuit, including the third wire to, uniting the springjack frames, remains unchanged. The elements also of the several spring-jacks remain unchanged; but the mode in which the connections ofthe jack are arranged with respect to the two wires of the metallic circuit main line is made to differ, and both wires now lead through separable electric contacts in each jack. The circuit L, for example, leads by its Wire 1 through each jack J of its series, passing in each from the contact'sprin g s to the fixed contact If, and after reaching the final section of the board and passing through its annunciator at its wire 1 is retraced in reverse order through the jacks, passing in each from the fixed contact If to the spring-contact s, so that its route is from 1 to 8, jack J to the fixed contact 15, then by wire 2 to jack J through spring 8, fixed contact 15, wire 3, jack J through spring 5, and fixed contact t, then to wire l, annunciator a, wire 5, fixed contact 25 and spring 3 at jack J wire 6, fixed contact 25 and spring .3 at jack J wire 7, fixed contact 25 and spring 3 of jack J, and thus to wire 1. The other circuits are similarly connected. It will be observed that returning through the switch-board the circuit passes in every case from. the fixed to the movable contact. WVit-h this construction whenever a connectingplug is introduced into the circuit its tip-conductor makes contact with the inner spring-contact s or whilethe first stem contact-piece 19 connects with the longer springs or 8 both spring-contacts being simultaneously disconnected from their resting contacts 25, whereby the jacks of all sections in an inward direction through the switch -board are cut off or entirely disconnected on both sides of the circuit, the line out connecting by both conductors to the plug-conductors and having both of its conductors open immediately beyond, so that any disturbance which may tend to be set up in the cut-off portion by static induction is in any event prevented from reaching the main-line talking-circuit and is therefore harmless. Switch-board cross-talk is in this way totally prevented.

I claim as my invention- 1.. A busy-test system for metallic-circuit multiple switch-boards, consisting in a series of metal spring-jack frames or plug-sockets for each circuit, supporting but insulated from spring contacts or terminals representing the conductors of said circuit, an independent conductor for each circuit extending between the several spring-jacks of saidcircuit and uniting electrically the insulated metal frames thereof, plug-connectors adapted to be inserted in the said plug-sockets and each provided with independent insulated contact-pieces at its tip and stem arranged to connect with the circuit-terminals, a third contact-piece arranged to connect with the plug-socket frames, a testing-battery having one of its poles in permanent connection with the said third contact-piece, and a telephone or similar testing-instrument detachably con nected in circuit with the said tip contactpiece and with the return-comluctor of said battery, substantially as described.

2. In a metallic-circuit multiple-switchboard busy-test apparatus, the combination of a series of triple-contact connection devices for each main metallic circuit, one at each section of the said switch-board, two of the said contacts being terminals, respectively, of the two conductors of the said metallic circuit, and the third of all of the said series being electrically united to form together part of a local test-circuit normally open at two points, the said three contacts being in each device insulated from one an-- other, a test-battery included in said normally-open local circuit, conducting devices in pairs, substantially as indicated herein, for uniting at any switch-board section the two main-conductor terminal contacts of one of the said connection devices with those of any other and for simultaneously closing the said local test-circuit at one point, and a telephone at each switch-section connected by one of its terminals with the said local circuit and provided at its other terminal with a contactmaker whereby the local test-circuit may be closed at its second normally open point through the said telephone and be enabled to give a busy-test signal therein at a switchsection differing from that where it was first closed, for the purposes specified.

3. In a metallic circuit multiple switchboard, two conductors extending from section to section of said board to constitute the direct and return conductors of a metallic main circuit and both provided at each section with connection terminals whereby they may be united to other circuits, a third conductor for each metallic circuit extending also between the sections of said switch-board and uniting a series of independent terminals insulated from but closely associated with the said pairs of line-terminals, metallic-circuit plug and cord conductors at each switchboard section for connecting the terminals of any two circuits, a contact-surface on each plug adapted to connect with the independent switch-board terminals when the said plug is employed to effect a line connection, a third conductor in each plug-cord connecting the same with one pole of a test-battery, and .a telephone bridged between the two main conductors connecting any two plugs and connected also with the return-conductor of said battery, substantially as described.

4. The combination of a multiple switchboard, terminal contacts at the sections of In testimony whereof I have signed my said switch-board for the incoming metallic name to this specification, in the presence of line-circuits, connectors or plugs in pairs havtwo subscribing Witnesses-this 8th day of ing contacts and conducting-wires for unit- August, A. D. 1891. 5 ving two line-circuits, aseparate wire for each metalllic circuit connecting the several sec- FRANK A. PIOKERNELL. tions of the switch-board, and a corresponding test-circuit having terminal contacts at Witnesses: said connectors or plugs, substantially as and T. W. DUNBAR,

I0 for the purpose described. O. J. PIOKERNELL. 

